Jailbreak has been available for WP8 for some time now on the ATIV S. With jailbreak i've been able to:
- Enable 3 Columns Start Screen, honestly made the start screen that much better.
- Switch the Search Key to open the Google Search app instead of Bing.
- Installed a patched but working version of Official YouTube client from MS.
- Enable Big Screen Mode
- Change the Boot Screen.
- Enabled Native File Explorer.
- Install Nokia Exclusive apps.
- CUSTOM TONES FOR EVERY SINGLE NOTIFICATION (ala WinMo 6.5)
- Allowed me to install GDR2+3 and bypass carrier approval.
None of these changes have decreased the stability of the os. it's still just as secure as before. Jailbreak will not allow the piracy of apps, as all XAP installers from the WindowsPhone Marketplace are signed. You cannot push signed XAP's to Windows Phone. As far as i am aware there is no 3rd party respository for WP apps, so Piracy is still a non issue.
I do not understand why so many are against jailbreaking. It does not reduce the integrity of the product but enhances it.